1. Field of the Invention and Related Art Statement
This invention relates to a method of measuring a concentration of substances contained in a sample by using a specific reaction between the substances in the sample and substances which are specifically reactive with the substances in the sample.
Such a specific reaction may be an immunological reaction between antigens and antibodies and a specifically bounding reaction, e.g., between biotin and avidin.
There has been proposed a method of measuring a concentration of substances contained in a sample by utilizing a power spectrum density of a fluctuation in intensity of scattered light. Such a method has been disclosed in Japanese Patent Application Laid-open Publication No. 61-28,866, corresponding to U.S. Pat. application Ser. No. 754,272 filed on July 12, 1985. In this method, the concentration is measured by utilizing the fact that a concentration of antigen or antibody substances is intimately related to a relaxation frequency of the power spectrum density of the fluctuation in intensity of light scattered from an antigen-antibody reaction liquid. That is to say, in this method, after the power spectrum density is derived, its relaxation frequency is derived, and finally the concentration is derived from the relaxation frequency.
In the method mentioned above, in order to measure the concentration of substances in a precise manner, it is necessary to derive the relaxation frequency accurately. However, it is difficult in practice to determine the relaxation frequency from a very wide frequency range.